The present invention relates to an ultrasonic nebulizer for nebulizing, or atomizing a liquid, and particularly to such nebulizers as are commonly used in air humidifiers, air heaters, and the like.
One known type of ultrasonic nebulizer includes an ultrasonic device (e.g., a piezoelectric crystal) which is immersed in the liquid (e.g., water) to be nebulized and which produces a spout of highly-agitated liquid. This type of nebulizer requires a large amount of energy because of the need to agitate a large body of liquid. The electronic circuit for supplying the ultrasonic device is therefore large and expensive. In addition, this type of nebulizer requires a liquid-level sensor to turn-off the power to the ultrasonic device if the liquid level drops below the ultrasonic device, to prevent its burn-out.
Another type of ultrasonic nebulizer includes an ultrasonic nebulizer nozzle and a container for the liquid to be nebulized, which container is disposed above the nozzle and includes a capillary tube for feeding the liquid from the bottom of the container to the nozzle by gravity. While such a nebulizer requires less energy than the immersion type, and therefore a simpler and less expensive power supply, the rate of feeding of the liquid via the capillary tube is difficult to control; moreover, the capillary tube tends to clog.